This invention relates generally to wrenches and, more particularly, to internal wrenches for use in the internal wrenching of mechanical joints.
Internal polygon shapes have been used in the past as a means of tightening mechanical fasteners, such as bolts, etc. A common type of these internal tightening means is the hexagonal shape used in the head of a bolt. These bolt type fasteners generally use solid hexagonal bar-like wrenches, known as Allen wrenches, to tighten and loosen them. Other polygonal shapes, such as a square, have also been used as a means to tighten mechanical fasteners and, in fact, except for a circle, any shape can be employed, including elipses, splines, etc.
Further, my U.S. Pat. Nos. 4,885,850 and 4,889,369 and pending applications Ser. No. 420,891, filed Oct. 13, 1989, Ser. No. 439,885, filed Nov. 20, 1989, and Ser. No. 448,762, filed Dec. 11, 1989 provide a teaching of how internal wrenching can be effectively employed in fluid flow components.
It is the general object of this invention to provide an internal wrench for use in wrenching mechanical joints, and particularly for use in the internal wrenching of fluid flow components of the above-indicated type.
Another object of the invention is to provide a method of turning a part, such as the fluid flow components in my above-mentioned patents, having an internal wrenching surface by using an internal wrench of the below-described construction.
Briefly stated, the internal wrench in accordance with the invention comprises a wrench body having an internal hole having polygonal shaped sides and of a length to transmit the torque required from the driver. The wrench body also has an outer polygonal shape which conforms to the part to be driven and is of an adequate length to transmit the necessary torque. In addition, there is provided a locating or positioning shoulder for ensuring the proper drive engagement in through-hole or torque limiting and/or drive disarming applications.
More specifically, the internal wrench in accordance with the invention comprises a wrench body having an internal hole centered on a longitudinal axis of the wrench body, said internal hole having a polygon shape providing a plurality of inner surfaces centered on the longitudinal axis and adapted to be contacted by a driver for the wrench. The wrench body has an outer driving surface providing a plurality of outer surfaces adapted to contact the internal wrenching surface of the part to be wrenched. The wrench body also includes a shoulder formed at one end thereof extending radially outwardly of the outer surfaces of the wrench body for contacting the part to be wrenched to limit the insertion of the wrench body into the parts internal wrenching surface to thereby locate the wrench in a driving position. The internal surfaces of the internal hole have surface portions which, along with the outer surfaces of the driving surface, extend axially from the radial plane of said shoulder at one end of the wrench body a substantial distance toward the other end of the wrench body. The surface portions of the internal surfaces are contained radially within the outer surfaces along a common portion of the longitudinal axis so as to be longitudinally coaxial therewith so that during the wrenching of a part by a driver in driving contact with said surface portions of said inner surfaces, wrenching forces are transmitted directly radially outwardly from said surface portions of said inner surfaces of said internal hole to said outer surfaces of said driving surface.
In the method in accordance with the invention of internal wrenching a component of a mechanical joint including a part having an internal wrenching surface, the first step is to provide an internal wrench of the type described above. Also in accordance with the method there is included the steps of inserting the internal wrench in a wrenching position by placing the outer surfaces of the wrench body in driving contact with the internal wrenching surface of said part for driving the same during wrenching and by placing the shoulder of the wrench body in contact with said part to limit the insertion of the wrench body into the part's internal wrenching surface to thereby locate the wrench in a driving position, placing the drive portion of a drive wrench into driving contact with the internal surfaces of said internal hole of the wrench body, and causing a turning movement of the drive portion of the drive wrench to cause a corresponding turning of the internal wrench whereby wrenching forces are transmitted directly radially outwardly from said surface portions of said inner surfaces of said internal hole to said outer surfaces of said driving surface.